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12.15.10: Mesoscale and submesoscale structure in the density field in OFES

I look here at the spatial structure of the potential density field σ in the 1/10th and 1/30th deg. OFES simulations. Fig. 1 shows σ for two different snapshots (one in Winter, one in Summer) at 162 m and Fig. 2 shows the single snapshot of σ available (Jan. 1 2001) at 151 m. We can see that in both cases, the submesoscale structure cannot be described as being composed of filaments. The structure is more complicated than that.


Figure 1: σ at 162 m in the 1/10th deg. OFES simulation: (a) on Jan. 3, 2004 and (b) on July 1, 2004.


Figure 2: σ at 151 m in the 1/30th deg. OFES snapshot (Jan. 1, 2001).

The upper panel of Fig. 3 shows the zonal and vertical section of σ in the 1/30th deg. OFES simulation west of the WHOTS location. The lower panel reproduces the section but as if the density was propagating westward through the WHOTS mooring at a speed of 8 cm/s (this is the speed estimated from AVISO SSH; see this note). Even if the seasonal cycle is absent, there are short events of shallow isopycnal surfaces that appear to be similar to those of the WHOTS observations (see this note). For completion, I also provide in Fig. 4, the Rossby number. Except between day 300 and 320, all large Rossby number are found within the surface mixed layer (upper 80 m).


Figure 3: (a) σ west of the WHOTS mooring in the 1/30th deg. OFES snapshot. (b) Same as in (a) but in time, assuming that the structures are propagating westward with a speed of 8 cm/s.


Figure 4: Same as in Fig. 3b except for the Rossby number.